This application proposes a study of the three dimensional structure of proton translocating ATPases. Single crystal X-ray diffraction techniques will be used to obtain and interpret a high resolution (3.5 Angstrom units electron density map of the F1 - sector of rat liver mitochondrial ATPase using the crystals obtained in this laboratory. It is also proposed to locate the binding sites for nucleotides, inhibitors and activators of the molecule using difference electron density maps.